Medical robotic systems such as those used in performing minimally invasive surgical procedures offer many benefits over traditional open surgery techniques, including less pain, shorter hospital stays, quicker return to normal activities, minimal scarring, reduced recovery time, and less injury to tissue. Consequently, demand for minimally invasive surgery using such medical robotic systems is strong and growing.
Examples of medical robotic systems include the davinci® Surgical System and the davinci® S™ Surgical System from Intuitive Surgical, Inc., of Sunnyvale, Calif. Each of these systems includes a surgeon's console, a patient-side cart, a high performance three-dimensional (“3-D”) vision system, and Intuitive Surgical's proprietary EndoWrist™ articulating instruments, which are modeled after the human wrist so that when added to the motions of the robotic arm assembly holding the surgical instrument, they allow at least a full six degrees of freedom of motion, which is comparable to or even greater than the natural motions of open surgery.
The patient-side cart typically includes three or more robotic arm assemblies each having a slave manipulator for holding and manipulating a medical device such as a surgical instrument or image capturing device for performing and viewing a medical procedure at a surgical site within a patient. To manipulate these medical devices, the surgeon's console also includes master input devices which may be selectively associated with the slave manipulators to manipulate their respectively held medical devices.
Whenever one of the slave manipulators reaches one or more of its workspace limits, the surgeon loses control of corresponding degrees of freedom movement of the medical device being held by that slave manipulator. Thus, unless special action is taken by a master-slave control system, operator manipulation of the associated master input device does not produce the expected response for the slave manipulator and/or its held medical device. Further, the slave manipulator response in this case may prove to be not only unintuitive to the surgeon, but also unpredictable and potentially dangerous during a surgical procedure.
One approach to mitigate this problem is to provide haptic feedback back to the master input device so as to urge the surgeon away from the workspace limitation. Although highly effective, such an approach may still be improved upon to not only ensure operation within workspace limitations, but also to provide operation that does not result in unintuitive or surgically dangerous responses.